C-13-depleted biphytanic diacids as tracers of past anaerobic oxidation of methane

摘要

C-13-depleted biphytanic diacids containing 0-2 pentacyclic rings are abundant biomarkers in Cenozoic methane seep limestones. The strong C-13 depletion (-132 to -96 parts per thousand) suggests that they derive from euryarchaea metabolizing methane. They occur with other biomarkers typically associated with anaerobic oxidation of methane, such as crocetane, pentamethylicosane (PMI), archaeol, hydroxyarchaeol and glycerol dibiphytanyl glycerol tetraethers (GDGTs). In contrast to GDGT-derived biphytane hydrocarbons, the biphytanic diacids appear to be almost exclusively derived from methanotrophic euryarchaea. (c) 2007 Elsevier Ltd. All rights reserved.